1. Field of the Invention
The invention relates to an air venting tube for an automobile lamp, more particular to an air venting tube which permits moisture and steam to escape from a housing of the automobile lamp, while effectively preventing entry of water into the housing of the lamp in order to prevent accumulation of water in the latter.
2. Description of the Related Art
When an automobile is disposed in a very humid environment for a period of time, moisture will enter into an interior of a housing of an automobile lamp of the automobile. When the automobile lamp is turned on, the moisture will turn into steam or fog, which results in a reduction in the brightness of the light output of the automobile lamp. As such, the conventional automobile lamp is generally provided with an air outlet in the housing thereof such that steam or moisture can escape from the housing to prevent a reduction in the brightness of the light output.
A plurality of quality tests are conducted for testing various properties of an automobile lamp after manufacturing the same. These tests include a spraying test through which the waterproofing effect of the automobile lamp is tested. The spraying test is performed by spraying the automobile lamp with a plurality of water jets in various directions for a period of time, and inspecting whether or not the automobile lamp has accumulated water within the housing thereof. It is noted that the aforementioned air outlet formed in the housing of the automobile lamp can permit water to enter into the interior of the housing of the automobile lamp during the spraying test. To solve this problem, an air venting tube has been proposed. The air venting tube is to be mounted on the housing at the air outlet to permit moisture and steam to escape from the housing of the automobile lamp, while preventing the entry of water into the housing of the lamp.
Referring to FIG. 1, a first conventional air venting tube 1 is shown to have an inverted L-shaped construction with a horizontal first section 11 and a vertical second section 12 which extends downwardly from the first section 11 generally at a right angle. The first section 11 is to be sleeved fittingly on a tubular air outlet 21 formed in a housing 20 of an automobile lamp 2. The second section 12 has an open lower end 121 with a bevel end face that is inclined with respect to a horizontal plane. However, the air venting tube 1 does not render the automobile lamp 2 to pass the spraying test since water can be guided directly upward via the open lower end 121 of the second section 12 and is allowed to enter the housing 20 of the lamp 2 through a vent hole 211 formed in the air outlet 21.
FIG. 2 illustrates a second conventional air venting tube 3 which is formed to have a U-shaped construction with a horizontal first section 32 to be sleeved fittingly on the tubular air outlet 21 in the housing 20 of the automobile lamp 2, a vertical second section 33 extending downwardly from the first section 32, and a horizontal third section 31 extending from the second section 33. However, it is found that the air venting tube 3 cannot effectively prevent entry of water into the interior of the housing 20 of the automobile lamp 2 through the air outlet 21 during the spraying test.
Although each of the aforesaid conventional air venting tubes 1, 3 is formed as a bent tubular body in order to block the water jets and prevent the entry of water into the housing 20 of the automobile lamp 2, the waterproofing effect achieved thereby is found to be unsatisfactory.
Referring to FIG. 3, a third conventional air venting tube 4 is shown to have a generally inverted L-shaped construction with a horizontal first section 43 to be sleeved fittingly on the tubular air outlet 21 in the housing 2 of the automobile lamp 2, and a vertical second section 44 which has an open lower end 42 with a bevel end face 421, similar to the first conventional air venting tube 1 shown in FIG. 1. An inclined cover plate 41 is formed in the lower end 42 and extends downwardly along the end face 421 from a circumferential edge part of the lower end 42 toward an axis of the second section 44. A blocking wall 45 is formed inside the second section 44, and extends from an inner wall surface of the second section 44. The blocking wall 45 is spaced apart vertically and is opposite to the cover plate 41, and inclines downwardly in a direction toward the axis of the second section 44. With the provision of the cover plate 41 and the blocking wall 45, the air venting tube 4 can achieve a better waterproofing effect in comparison with the conventional air venting tubes 1 and 3 shown in FIGS. 1 and 2.
Referring to FIGS. 3 and 4, during the manufacture of the air venting tube 4, an inner mold 40 with a shape corresponding to that of the interior of the air venting tube 4 is disposed within and is spaced apart from an outer mold 46. As shown, in order to form the cover plate 41 and the blocking wall 45, the inner mold 40 needs to be cut to form a first groove 401 and a second groove 402. Since each of the grooves 401, 402 extends radially into the inner mold 40 toward the axis of the inner mold 40, it is required that the grooves 401, 402 be spaced apart by a predetermined distance to prevent breakage of the inner mold 40. As such, in the air venting tube 4, a vertical distance (a) and a horizontal clearance (b) are defined between distal ends of the cover plate 41 and the blocking wall 45.
However, during the spraying test, it is found that the clearance (b) unavoidably permits entry of the water jets upward into the interior of the air venting tube 4. For example, when the spraying test is performed to test the waterproofing effect provided by the air venting tube 4 whose clearance (b) is 1 mm, with a water pressure of 3 kg and a spraying period of 2 hours, water was found to have accumulated in the housing 20 of the automobile lamp 2. The waterproofing effect provided by the air venting tube 4 is still unsatisfactory.